138 research outputs found
Rotor-to-stator Partial Rubbing and Its Effects on Rotor Dynamic Response
Results from experimental and analytical studies on rotor to stationary element partial rubbings at several locations and their effects on rotor dynamic responses are presented. The mathematical model of a rubbing rotor is given. The computer program provides numerical results which agree with experimentally obtained rotor responses
Influence of rubbing on rotor dynamics, part 1
The results of analytical and experimental research on rotor-to-stationary element rubbing in rotating machines are presented. A characterization of physical phenomena associated with rubbing, as well as a literature survey on the subject of rub is given. The experimental results were obtained from two rubbing rotor rigs: one, which dynamically simulates the space shuttle main engine high pressure fuel turbopump (HPFTP), and the second one, much simpler, a two-mode rotor rig, designed for more generic studies on rotor-to-stator rubbing. Two areas were studied: generic rotor-to-stator rub-related dynamic phenomena affecting rotating machine behavior and applications to the space shuttle HPFTP. An outline of application of dynamic stiffness methodology for identification of rotor/bearing system modal parameters is given. The mathematical model of rotor/bearing/seal system under rub condition is given. The computer program was developed to calculate rotor responses. Compared with experimental results the computed results prove an adequacy of the model
Influence of rubbing on rotor dynamics, part 2
Rotor dynamic behavior depends considerably on how much the specific physical phenomena accompanying rotor rubbing against the stator is involved. The experimental results of rotor-to-stator rubbing contact are analyzed. The computer code is described for obtaining numerical calculations of rotor-to-stator rubbing system dynamic responses. Computer generated results are provided. The reduced dynamic data from High Pressure Fuel Turbo Pump (HPFTP) hot fire test are given. The results provide some significant conclusions. Information is provided on the electronic instrumentation used in the experimental testing
Some Remarks on Theories with Large Compact Dimensions and TeV-Scale Quantum Gravity
We comment on some implications of theories with large compactification radii
and TeV-scale quantum gravity. These include the behavior of high-energy
gravitational scattering cross sections and consequences for ultra-high-energy
cosmic rays and neutrino scattering, the question of how to generate naturally
light neutrino masses, the issue of quark-lepton unification, the equivalence
principle, and the cosmological constant.Comment: 28 pages, Late
Atypical composition and ultrastructure of proteoglycans in the mouse corneal stroma
PURPOSE: Recently, gene-targeted strains of mice with null mutations for specific proteoglycans (PGs) have been used for investigations of the functional role of these molecules. In the present study, the corneal stroma of the mouse was examined to provide some baseline PG morphologies in this species.
METHODS: Monoclonal antibodies to specific glycosaminoglycan (GAG) chain sulfation patterns were used to characterize PG composition in corneal extracts by SDS-PAGE and Western blot analysis and to identify their tissue distribution by immunofluorescence microscopy. PGs were also visualized by transmission electron microscopy after contrast enhancement with cationic dye fixation.
RESULTS: Western blot analysis of pooled corneal extracts and immunofluorescence of tissue sections identified 4-sulfated, but not 6-sulfated, chondroitin sulfate/dermatan sulfate (CS/DS). Keratan sulfate (KS) was present only as a low-sulfated moiety. Electron microscopic histochemistry disclosed a complex array of corneal PGs present as (1) fine filaments radiating from collagen fibrils, and (2) elongate, straplike structures, running either along the fibril axis or weaving across the primary fibril orientation. These large structures were digested by chondroitinase ABC, but not by keratanase.
CONCLUSIONS: KS in the mouse is predominantly undersulfated and generates an immunostaining pattern that differs from that observed in corneas of other mammalian species thus far investigated. The mouse cornea resembles other mammalian corneas in the presence of filamentous arrays of small, collagen-associated stromal PGs visualized by cationic dye staining. However, large dye-positive structures with a CS/DS component are also present and appear to be unique to the cornea of this species
First bounds on the very high energy gamma-ray emission from Arp 220
Using the Major Atmospheric Gamma Imaging Cherenkov Telescope (MAGIC), we
have observed the nearest ultra-luminous infrared galaxy Arp 220 for about 15
hours. No significant signal was detected within the dedicated amount of
observation time. The first upper limits to the very high energy -ray
flux of Arp 220 are herein reported and compared with theoretical expectations.Comment: Accepted for publication in Ap
MAGIC observations of very high energy gamma-rays from HESS J1813-178
Recently, the HESS collaboration has reported the detection of gamma-ray
emission above a few hundred GeV from eight new sources located close to the
Galactic Plane. The source HESS J1813-178 has sparked particular interest, as
subsequent radio observations imply an association with SNR G12.82-0.02.
Triggered by the detection in VHE gamma-rays, a positionally coincident source
has also been found in INTEGRAL and ASCA data. In this Letter we present MAGIC
observations of HESS J1813-178, resulting in the detection of a differential
gamma-ray flux consistent with a hard-slope power law, described as dN/(dA dt
dE) = (3.3+/-0.5)*10^{-12} (E/TeV)^{-2.1+/-0.2} cm^(-2)s^(-1)TeV^(-1). We
briefly discuss the observational technique used, the procedure implemented for
the data analysis, and put this detection in the perspective of multifrequency
observations.Comment: Accepted by ApJ Letter
Discovery of VHE Gamma Radiation from IC443 with the MAGIC Telescope
We report the detection of a new source of very high energy (VHE, E_gamma >=
100GeV) gamma-ray emission located close to the Galactic Plane, MAGIC
J0616+225, which is spatially coincident with SNR IC443. The observations were
carried out with the MAGIC telescope in the periods December 2005 - January
2006 and December 2006 - January 2007. Here we present results from this
source, leading to a VHE gamma-ray signal with a statistical significance of
5.7 sigma in the 2006/7 data and a measured differential gamma-ray flux
consistent with a power law, described as dN_gamma/(dA dt dE) = (1.0 +/-
0.2)*10^(-11)(E/0.4 TeV)^(-3.1 +/- 0.3) cm^(-2)s^(-1)TeV^(-1). We briefly
discuss the observational technique used and the procedure implemented for the
data analysis. The results are put in the perspective of the multiwavelength
emission and the molecular environment found in the region of IC443.Comment: Accepted by ApJ Letter
Unfolding of differential energy spectra in the MAGIC experiment
The paper describes the different methods, used in the MAGIC experiment, to
unfold experimental energy distributions of cosmic ray particles (gamma-rays).
Questions and problems related to the unfolding are discussed. Various
procedures are proposed which can help to make the unfolding robust and
reliable. The different methods and procedures are implemented in the MAGIC
software and are used in most of the analyses.Comment: Submitted to NIM
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